1. Field of the Invention
This invention relates generally to tools used to complete subterranean wells. More particularly the present invention describes a means of perforating, gravel pack completing, testing, and abandoning a well in a single trip.
2. Description of Related Art
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production testing of the well can begin.
Sand or silt flowing into the wellbore from unconsolidated formations can lead to an accumulation of fill within the wellbore, reduced production rates and causing damage to subsurface production equipment. Migrating sand has the possibility of packing off around the subsurface production equipment, or may enter the production tubing and become carried into the production equipment. Due to its highly abrasive nature, sand contained within production streams can result in the erosion of tubing, flowlines, valves and processing equipment. The problems caused by sand production can significantly increase operational and maintenance expenses. The loss of sand from the formation can create void areas and undermine the formation stability, and this can lead to formation collapse and to a total loss of the well""s productive capacity. One means of controlling sand production is the placement of relatively large sand (i.e., xe2x80x9cgravelxe2x80x9d) around the exterior of a slotted, perforated, or other type liner or screen. The gravel serves as a filter to help assure that formation fines and sand do not migrate with the produced fluids into the wellbore. In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the unconsolidated formation that is to be completed for production. The screen is typically connected to a tool that includes a production packer and a cross-over, and the tool is in turn connected to a work or production tubing string. The gravel is pumped in a liquid slurry down the tubing and through the cross-over, thereby flowing into the annulus between the screen and the wellbore. The liquid forming the slurry leaks off into the formation and/or through the screen, which is sized to prevent the gravel in the slurry from flowing through. The liquid that passes through the screen flows up the tubing and then the cross-over directs it into the annulus area above the packer where it can be circulated out of the well. As a result of this operation, the gravel is deposited in the annulus area around the screen where it forms a gravel pack. The screen prevents the gravel pack from entering into the production tubing. It is important to size the gravel for proper containment of the formation sand, and the screen must be designed in a manner to prevent the flow of the gravel through the screen.
At times it is desirable to complete a zone, perform production tests and then abandon the well, either temporarily or permanently. Offshore exploration wells are often drilled, completed and then flow tested to gain information on the productive capabilities of the field and the extent of the potential recoverable reserves. As there are usually no production facilities, platforms or pipelines in place when these exploration wells are drilled, they must be abandoned following the flow testing. Field development, if it is commenced at all, may occur several years after the discovery well is tested and abandoned. Field development can include the design and construction of fixed or floating production facilities, pipeline design and construction to transport the product to market, and detailed reservoir studies to determine the most economical development plan and the most efficient production rates that can be achieved.
Current methods to complete a well, perform flow tests and then abandon the well involve a number of trips in and out of the well. For example, one trip can be used to perforate the well, another trip can place the sand screens and perform the gravel pack operation, and yet another trip may be required to plug and abandon the well. Each trip in and out of the wellbore results in increased time and expense. Any reduction in the number of trips required to perform these procedures will result in significant cost savings.
There is a need for improved tools and methods to enable an operator to complete a well, perform flow tests and then abandon the well.
One embodiment of the present invention is a completion apparatus for perforating, completing, testing, and abandoning a wellbore in a single trip that comprises a perforating gun, a sand screen, an isolation valve, a packer, and a workstring. The perforating gun, sand screen, isolation valve and packer can be directly or indirectly mechanically attached to the workstring. The sand screen is typically located above the perforating gun, and the packer and isolation valve are both located above the sand screen and are releasably attached to the workstring. The perforating gun is capable of imposing perforations into a predetermined zone within the wellbore to create a perforated zone. The completion apparatus is longitudinally movable within the wellbore and is capable of positioning the sand screen assembly adjacent to the perforated zone in preparation of a gravel pack operation and flow testing. The workstring is capable of being released from the packer and the isolation valve, thus enabling removal of the workstring from the wellbore after gravel packing and flow testing have been performed.
The isolation valve is movable between an open position and a closed position and comprises a longitudinal flow path and a sealing mechanism whereby fluid flow through the longitudinal flow path is possible when the isolation valve is in its open position and fluid flow through the longitudinal flow path is restricted by the sealing mechanism when the isolation valve is in its closed position. The isolation valve is typically in its open position when the workstring is engaged with the packer and is in its closed position when the workstring is disengaged from the packer. The completion apparatus may also comprise a second packer located between the perforating gun and the sand screen. This second packer is capable of being set within the wellbore to isolate the zone to be perforated and to facilitate well testing subsequent to perforating.
The completion apparatus can further comprise a testing tool that is in communication with the workstring. The testing tool is capable of being located within the wellbore during well testing or can be attached to the well at the surface and capable of performing well testing operations.
Another embodiment of the invention is an apparatus for completing, testing and abandoning a well in a single trip into the wellbore. The apparatus comprises a perforating gun, a sand screen, a testing member and an isolation valve. The apparatus is longitudinally movable within the wellbore and is capable of positioning the perforating gun at a desired location to create a perforated zone and then capable of being re-positioned so that the sand screen is adjacent to the perforated zone. The isolation valve is capable of moving between an open and closed position, and when in its closed position is capable of isolating a perforated zone. The apparatus may further comprise a packer.
Yet another embodiment of the invention is a method of completing, testing, and abandoning a wellbore in a single trip that comprises perforating an interval within the wellbore, positioning a sand screen assembly adjacent the perforated interval, gravel packing the perforated interval, performing production testing on the perforated interval, and abandoning the wellbore, all in a single trip in the wellbore. The well can be killed with hydrostatic fluid pressure after the wellbore is perforated and after the production testing if it is needed. The method can further comprise inserting a tool assembly into the wellbore that includes a perforating gun, sand screen, and packer attached to a workstring, the sand screen being located above the perforating gun and the packer being located above the sand screen, and setting the packer prior to gravel packing the wellbore. Abandoning the wellbore comprises releasing the workstring from the packer and spotting plugs while removing the workstring from the wellbore. The plugs spotted within the wellbore comprise material circulated down the workstring, such as sand or cement. The method can further comprise closing an isolation valve after the well testing and prior to abandoning the wellbore. The above mentioned tool assembly can comprise an isolation valve that closes and isolates the perforated zone either prior to or in conjunction with the release of the workstring from the packer. The isolation valve is capable of restricting the flow of fluids from the formation through the packer. A second packer may be located below the sand screen assembly and above the perforating gun, and set prior to gravel packing. This second packer set below the sand screen can isolate the sand screen from the portion of the wellbore below the perforated zone, sometimes referred to as a sump. Having the sand screen isolated from the sump area will generally enable a better gravel pack than would be achieved if the sump area were left open to the sand screen and the perforated interval.
Yet another embodiment of the invention is a method of completing, testing, and abandoning a wellbore comprising inserting a tool assembly into the wellbore. The tool assembly comprises a perforating gun, a retrievable packer, a sand screen assembly, a permanent packer, and an isolation valve on a workstring. The method involves positioning the perforating gun at a predetermined location within the wellbore, setting the retrievable packer, perforating the wellbore and creating a perforated zone. The retrievable packer is then released, the tool assembly repositioned to place the sand screen assembly substantially adjacent to the perforated zone and the retrievable packer located below the sand screen assembly is set. The permanent packer located above the sand screen assembly is set and a gravel pack operation is performed adjacent the sand screen assembly thereby depositing a gravel pack in the annulus area between the sand screen assembly and the perforated zone. Testing of the perforated zone is then performed. After testing the isolation valve is closed, the workstring is released from the permanent packer, and the wellbore is abandoned while pulling the workstring out of the wellbore. All of the above steps occur in a single trip into the well.
The perforated zone can be flowed back after the well has been perforated if that is desired. If needed, the well can be temporarily killed with hydrostatic fluid pressure prior to releasing the retrievable packer and prior to releasing the workstring from the permanent packer.